Konrad Hughen is a paleoclimatologist in the WHOI Department of Marine Chemistry and Geochemistry. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)

Paleoclimate records from Greenland, the Mediterranean, and the Cariaco Basin off Venezuela reveal synchronous changes in climate throughout the North Atlantic region over the last 55,000 years. The pink bands show the three proposed time windows for the last appearance of Neanderthal in the fossil record. (Tzedakis et al, as published in the journal Nature)

Extinction of Neanderthals Was Not a Climate Disaster Scenario

New Research Reveals That Abrupt Climate Change Was Not the Primary Cause of Species Disappearance

For the past few decades, scientists have offered several competing
theories for what led to the extinction of the Neanderthals, with much of the
debate focusing on the relative roles of climate change versus conflict with
modern humans. Now one theory can be ruled out.

New research by a multidisciplinary, international teamincluding
paleoclimatologist Konrad Hughen of the Woods Hole Oceanographic
Institutionshows that Neanderthals did not die out at a time of extreme and
sudden climatic change, as some researchers have suggested.

Comparing the dates of the final Neanderthal occupation of
Gorham’s Cave on Gibraltar with paleo-climatological records drawn from
Greenland ice cores and from Atlantic seafloor sediments, Hughen and colleagues
concluded that two proposed dates (roughly 28,000 and 32,000 years ago) both
fall within climate intervals that were not particularly cold or otherwise severe.

Specifically, the proposed dates do not coincide with what scientists know as
"Heinrich Events," when vast quantities of icebergs spilled into the North
Atlantic, blanketed it with fresh water, and disturbed oceanic and
atmospheric circulation to cause abrupt climate changes.

Another more controversial proposal suggests that the last
Neanderthals may have died out as recently as 24,000 years ago. If that
timeline is true, it did coincide with a period of major climate shifting, but
the changes were much more gradual and incremental, possibly allowing them to
adapt and migrate as they had done before.

The younger date “would imply a
greater role of climate in Neanderthal extinction, not necessarily directly but
perhaps in the form of climate-driven intensified competition as a result of
increased southward human migration from higher latitudes," the scientists
wrote.

The research analysis was led by Chronis Tzedakis of the University of Leeds;
with contributions from Hughen, Isabel Cacho of the University of Barcelona,
and Katerina Harvati of the Max Planck Institute for Evolutionary Anthropology.
The results were published in the September 13 issue of the journal Nature.

Although scientists have been expanding the records of past
climate, correlating them with anthropological and archaeological findings has
often been difficult. Tzedakis noted that “there are three main limitations to
understanding the role of climate in the Neanderthal extinction: uncertainty
over the exact timing of their disappearance; uncertainties in converting
radiocarbon (14C) dates to actual calendar years; and the
chronological imprecision of the ancient climate record.”

“Our method circumvents the last two problems,” said Hughen.
Basically, the researchers did not attempt to relate the dates of the
disappearance of Neanderthals to a calendar year, but directly to what the
climate record tells us about the environment.

From ice cores and sedimentary
records, Hughen and other paleoclimatologists can derive information about past
temperatures and the amount of moisture in the atmosphere to paint a general
picture of global climate. Radiocarbon-dated events may be difficult to
calibrate exactly with calendar years, but geologic, climatological, and paleontological
records can be mapped to each other.

“In this case, we were able to provide a much more accurate
picture of the climatic background at the time of the Neanderthal disappearance,”
Hughen added. “Our approach offers the potential to unravel the role of climate
in critical events of the recent fossil record, as it can be applied to any
radiocarbon date from any deposit.”

Funding for Konrad Hughen’s research was provided by the National Science
Foundation.

Woods Hole Oceanographic Institution is a private, independent organization
in Falmouth, Mass., dedicated to marine research,
engineering, and higher education. Established in 1930 on a recommendation from
the National Academy of Sciences, its primary mission is to understand the
oceans and their interaction with the Earth as a whole, and to communicate a
basic understanding of the ocean's role in the changing global environment.

Originally published: September 26, 2007

WHOI is the world's leading non-profit oceanographic research organization. Our mission is to explore and understand the ocean and to educate scientists, students, decision-makers, and the public.